Battery parts such as battery terminals, which are typically cold formed or die cast, are normally secured to a container with a portion of the battery terminal located inside the container and a further portion located outside the container. The battery containers, which are typically plastic such as polyethylene, are molded around a set of acid rings that are located on the portion of the terminal that is located within the container. The acid rings provide an extended interface and consequently a tortuous path to inhibit or prevent electrolyte from escaping from the battery container. Because the acid must follow an extended interface to escape this type of sealing, with a set of concentric acid rings, is often referred to as a labyrinth seal.
Because the battery terminals are cast or cold formed the radially protruding acid rings are generally formed with either a rectangular cross sectional shape or a slight outward taper to facilitate removal of the battery terminals from the mold.
While battery terminals have a generally rectangular cross sectional shape are used extensively other shaped acid rings have been used in order to prevent the plastic container from shrinking away from the terminal and upsetting the interface between the battery part and the container which could cause leakage of electrolyte. Generally, these type of acid rings provide lateral engagement between the acid ring and the container.
For example, the 1971 United Kingdom patent specification GB 1236495 discloses a battery terminal wherein two acid ring are bent toward each other to provide a dovetail shaped gap that extends along the entire length of the acid ring so that it enables the two adjacent acid rings to form a dovetail joint with the battery container and thereby provide lateral engagement between the acid ring and the container.
The 1971 United Kingdom patent specification GB 1,245,255 discloses three acid rings that have been deformed to create a dovetail shaped gap between adjacent acid rings with the dovetail gap extending along the entire length of the acid ring to form two dove tail joints with the container and thereby provide lateral engagement between the acid ring and the container. In this embodiment the acid rings are compressed sufficiently to deform the acid rings so that the acid ring tapers inwardly along the entire length of the ring, that is from the circumferential edge of the acid ring to the base of the acid ring.
The 1981 Japanese patent JP56159054 discloses a further embodiment wherein the battery terminal acid rings are deformed along the entire length of the acid ring to form inclined projections on the acid rings that engage the cover to provide effective liquid tightness and thereby provide lateral engagement between the acid ring and the container.
The 1993 Hofmann German patent DE 4127956 A1 discloses a battery terminal wherein the ends of the acid rings have been rounded and the lower acid ring has been provided with a wedge shaped profile to increase the sealing effect with a container and thereby provide lateral engagement between the acid ring and the container.
The 1994 Hofmann German patent DE 4241393 C1 discloses a battery terminal wherein the ends of the acid rings have been rounded and a barb or undercut that forms a hook which is located on the back side of the acid ring. The “hook” on the back side of the deformed acid ring hooks into the plastic container i.e. to lateral restrain the container to prevent the plastic battery container material from shrinking away from the battery terminal. In addition, a further embodiment is disclosed wherein adjacent acid rings are of the same thickness but are angled away from each other in order to laterally restrain the container with respect to the acid rings.
The 1992 Hofmann European patent 0 601 268 B1 discloses a battery terminal wherein the ends of the acid rings either have a rounded end or a triangular shaped end with a barb or hook on the back side of the acid ring. This “hook” on the back side of the deformed acid ring hooks the plastic to prevent the plastic battery container material from shrinking away from the battery terminal by laterally restraining the container with respect to the acid rings.
The 1992 Hofmann European patent application 0 601 268 A1 also discloses the battery terminal wherein the ends of the acid rings either have a rounded end or a triangular shaped end with a barb or undercut or hook on the back sides of the acid ring. In addition, a further embodiment of an acid ring is disclosed wherein two adjacent acid rings, which are of the same thickness, are angled away from each other to laterally restraining the container with respect to the acid rings by forming a dovetail like joint.
The 1989 Hofmann German patent application DE 3942175A1 discloses a method of forming a battery terminal with acid rings by cold rolling the terminal to form the circumferential acid rings.
Speigelberg U.S. Pat. No. 6,644,084 describes a process of forming an acid ring with a hook by first deforming the battery terminal from a rectangular shaped acid ring to an arrowhead shaped acid ring. The transformation to the hook shape is obtained by rotating the battery terminal relative to a cold forming roller to deform an acid ring with a rectangular cross section into an acid ring having an undercut or overhang. The cold rolling process involves substantial deformation of the acid ring on the cast battery part in order to produce the hook for engaging the battery container.
While the prior art provides acid rings with rectangular shapes that are either bent or transformed into a different shape by cold rolling to form a lateral restraint between the battery container and the terminal. The lateral restraint is obtained by either forming a hook on the acid ring or forming a dovetail or dovetail like engagement between the battery container and the battery terminal.
In contrast to the prior art acid rings, where the shape of the acid ring is substantially altered, in the present invention one can cast a battery part with the acid ring having a bifurcated end separated by a circumferential grove or an end with a single annular tapered lip. The bifurcated end results in two outwardly extending annular lips on each acid ring.
The annular lips on each acid ring can be flared away from each other to produce a beveled surface or sealing bead along an annular outer portion of each of the annular lips which not only laterally restrains the container with respect to the terminal but also forms an enhanced sealing region between the container and the acid ring. In addition the circuitous path provided by the bifurcated acid rings can increase the resistance to electrolyte leakage by providing a more tortuous interface between the acid rings and the container.
A further feature of the invention is the flaring of the lips can be obtained by applying a radial compressive force to the bifurcated ends of the acid ring. Since only the bifurcated ends of the acid ring are flared it substantially eliminates problems that can occur with prior art cold farming deformation of a pressure cast battery terminal. That is, an interface between a die cast portion of battery terminal and a cold rolled portion of the battery terminal can lead to cracks or stress areas between the cast region and the cold formed region of the battery part, which can be subject to electrolyte leakage therethrough. By minimizing the interface one can minimize the opportunity for leakage.
Thus the flaring of the lips on the bifurcated acid ring of the present invention produces a back flare sealing region that extends circumferential around the terminal which not only enhances sealing but also restrains lateral engagement between the container and the acid rings and at the same time minimizing the occurrences of fractures or stress cracks in metal that has a portion of the original die cast shape altered by cold rolled deformation.
The present invention provides a battery part that eliminates the substantial deformation or acid ring transformation necessary to either form an under cut or overhang on the acid ring or to deform an acid ring along its entire length to form a dovetail engagement as shown in GB 1236495; GB 1,245,255; JP 5619054 and EPO 06012681A1. In addition, the present invention further eliminates the need to mechanically deform the acid ring from a rectangular shape to an arrow head shaped acid ring or to an acid ring with a hook or an acid ring with a beveled surface that extends along the entire length of the acid ring as shown in EP006012681B1 and DE 4241393;
Thus, by flaring the lip or lips on the circumferential end of the acid ring one can form annular sealing regions, laterally restrain the container with respect to the acid ring, and inhibit electrolyte from escaping from the battery container with a more tortuous path. Not only does the present invention inhibit escape of electrolyte by providing a circumferential sealing ring it also make it easier to flow the plastic around the acid ring since the flared lip extends along only a portion of the acid ring. In addition, the present process minimizes stress produced in the battery part when a substantial part of a die cast battery terminal is subsequently transformed to a substantially different shape by cold rolling since the lips on the end of the acid ring can be flared instead of mechanically deformed into an entirely different shape.